Key cellular events related to the steroidogenic action of ACTH will be studied in rat adrenocortical cell suspensions. These events involve 1) ACTH binding to plasma membrane receptors, 2) calcium action in events after 1) involving activation of a possible protein component (contractile protein?) which leads to triggering off of the catalytic unit adenylate cyclase and cyclic-3', 5'-AMP (CAMP) production, 3) CAMP effects on glycolytic and Krebs-cycle enzymes and 4) sources of reducing equivalents (NADPH) required for the cytosolic and mitochondrial steroid hydroxylating enzymes. Comparative studies will be continued with normal and the slightly steroidogenic adrenocortical Snell 494 carcinoma cells to uncover information which would suggest approaches to the treatment of the tumor-bearing rats by immunotherapeutic (and other) means. This will involve isolation of trophic hormone receptor(s) from the plasma membrane of 494 cancer cells and subsequent generation of the antibody to the receptor(s) after injecting the protein receptor(s) into rabbits. The isolated antibody will then be injected into rats bearing tumor transplants to inhibit growth of these transplants into tumors. BIBLIOGRAPHIC REFERENECES: Cyclic AMP Response of Isolated Snell Adrenocortical Carcinoma 494 Cells to Trophic Hormones and Other Substances. Peron, F.G., Maudsley, D.V. and Haksar, A. Endocrine Research Comm: 2, 403, 1975. Lanthanum: Inhibition of ACTH-Stimulated Cyclic AMP and Corticosterone Synthesis in Isolated Rat Adrenocortical Cells. Haksar, A., Maudsley, D.V., Peron, F.G., and Bedigian, E. J. Cell Biology: 68, 142, 1975.